Various methods exist for the production of electronic grade silicon and silane, one of its precursors. These methods include processes for the purification of silane before its reaction (e.g., thermal decomposition) to produce electronic grade silicon. For example, see Walker et al. (U.S. Pat. No. 4,537,759), incorporated in its entirety herein, and the references therein.
Particular examples of silicon and silane contaminants of concern are carbon containing species such as ethylene and ethylsilane. Ethylsilane can be separated from silane by distillation, but ethylene is very difficult to remove due to the close boiling points of ethylene and silane.
Ethylene can be separated from silane by passing a mixture of ethylene and silane through molecular sieves. However, such molecular sieve process can produce ethylsilane, introducing the newly produced ethylsilane as a contaminant. Some steps can be performed to reduce ethylsilane formation. For instance, see commonly-assigned United States application, Ser. No. 07/516,315, filed by W. S. Park on Apr. 30, 1990. There still remains a need for practical separation of ethylsilane from silane.